In-tank type pump modules, which are accommodated in a fuel tank, are disclosed in JP-B2-2643436 (JP-A-2-277954) and JP-B2-2643461 (JP-A-3-50372). Each pump module includes a sub-tank. The sub-tank has a bottom wall, on which claws, which are resiliently deformable, are provided. The claws of the sub-tank contact the bottom wall of the fuel tank, so that the claws insulate vibration of a fuel pump that is accommodated in the sub-tank. Thus, noise due to vibration of the fuel pump is insulated.
However, the claws are small in the above structure, and the claws cannot sufficiently insulate vibration and noise. Therefore, a rubber sheet may be enlarged to entirely cover the bottom wall of the sub-tank, and the rubber sheet may be inserted between the bottom wall of the sub-tank and the bottom wall of the fuel tank to insulate vibration. However, the rubber sheet may swell due to contact with fuel, and stress may arise in the rubber sheet due to swelling. When the rubber sheet is large, the stress due to swelling may become large. As a result, the rubber sheet may be lifted relative to the sub-tank and the fuel tank, and vibration insulative property of the rubber sheet may be degraded.